Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered; the description adds genuinely new context by stating the call is free and requires no key, plus that the data reflects what is supported 'today'. It does not discuss how frequently the list changes or the shape of the response, keeping it below 5.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two tight sentences with zero waste: the first states what is returned, the second states when to call it and the cost/auth conditions. Nothing is buried or repeated.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a zero-parameter, read-only lookup with no output schema, the description covers what the result contains (currencies and corridor counts), the recommended call order, cost, and auth. Only the freshness/refresh cadence of the 'today' snapshot is left implicit.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool takes zero parameters, so the baseline is 4 and there is nothing for the description to disambiguate. No parameter-level detail is needed or missing.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description names the specific resource: every supported currency plus the count of directional corridors between them, which is a concrete verb-free but unambiguous listing purpose. It falls short of 5 because the sibling set contains several near-duplicates (coverage, get_coverage, swapeazi_corridor_registry) and the description never says how swapeazi_coverage differs from them.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It gives explicit sequencing guidance: call this before swapeazi_landed_cost to determine whether a pair is covered, which is exactly the kind of when-to-use direction agents need. It does not address the overlapping coverage/corridor_registry siblings or say when *not* to call it.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.